def add(x,y):
    z=x+y
    print('两数相加的和为%d:'%z)

def sub(x,y):
    z=x-y
    print('两数相减的和为%d:'%z)
PI=3.1415
city=['北京','上海','深圳']

if __name__=='__main__':
    r1=add(100,200)
    r2=sub(200,30)
    print('圆周率:',PI)
    print('城市列表:',city)